using System;

​

public class Node

{

    public int Value { get; set; }

​

    public Node Left { get; set; }

​

    public Node Right { get; set; }

​

    public Node(int value, Node left, Node right)

    {

        Value = value;

        Left = left;

        Right = right;

    }

}

​

public class BinarySearchTree

{

    public static bool Contains(Node root, int value)

    {

        if (root != null){            

            if (root.Value == value) {

                return true;        

            }

            else if (root.Value > value) {

                return Contains(root.Left, value);

            }

            else if (root.Value < value) {

                return Contains(root.Right, value);

            }

        }

        return false;        

    }

​

    public static void Main(string[] args)

    {

        Node n1 = new Node(1, null, null);

        Node n3 = new Node(3, null, null);

        Node n2 = new Node(2, n1, n3);

​

        Console.WriteLine(Contains(n2, 3));

    }

}